


Dancing With Myself

by SoloShikigami



Category: Undertale (Video Game)
Genre: Ecto-Genitalia, Fontcest, M/M, Plot What Plot/Porn Without Plot, Sans - Freeform, Underswap Sans, Undertail
Language: English
Status: Completed
Published: 2016-05-14
Updated: 2016-05-14
Packaged: 2018-06-08 06:39:51
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,668
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6843301
Author URL: https://archiveofourown.org/users/SoloShikigami/pseuds/SoloShikigami
Summary: <blockquote class="userstuff">
              <p>Underswap Sans has his eyes on his more subdued double and is just looking for some fun. But is Sans too oblivious or is he too focused on someone else?</p>
            </blockquote>





	Dancing With Myself

**Author's Note:**

> ... is it still incest if you're screwing yourself from an alternate universe?  
>  Requested by IggyCat95! Hope you like it!

Sans could feel his face heating up as his double jumped onto the small stage as if he owned it, grabbing the microphone confidently and all but tearing it off its stand. Both of their brothers, along with some of the members of the audience, cheered him on as this was his third song of the evening.

It wasn't that he didn't have a nice voice, because he did, but Sans knew it was more his song choice and his actions on stage.

This Sans knew his body well and how to move it. He had a handle on social nuances that Sans could only imagine, and speaking of imagination, he could only hope that the looks and winks the other Sans threw at him were part of the performance.

Why did Sans think this was a good idea?

~~~~~~~~~~~~~~~~~~~~~

"Come on, we should do something fun!"

Sans grunted as his hyperactive twin from another universe latched onto his back, his arms wrapping around his neck, the sudden weight unexpected.

"Got something in mind, Blueberry?" Sans asked.

"Hmph, told you don't call me that, call me Blue if you have to, but I'm not a berry."

"But it suits you!" Papyrus chimed in.

Blue let go of Sans and put his fists on his hips. "It's demeaning of someone in line to be part of the Royal Guard! How would you like it if your nickname was, I dunno, Cinnamon Bun or something?"

Blue's brother, Pappy, laughed. Papyrus thought about this for a moment.

"I think it's a bit long, and it doesn't roll off one's tongue like The Great Papyrus!"

"But would you actually want to be called that?"

Papyrus shrugged. "Could be worse?"

Blue rolled his eyes. "Anyway, I was thinking karaoke!"

"That doesn't sound like a bad idea," Sans said thoughtfully.

Blue all but squealed in delight.

~~~~~~~~~~~~~~~~~~~~~

It was weird finding your double attractive, if nothing else it screamed narcissism in the worst way. Sans was sure he was heading to some sort of special hell anyway, since he was harboring similar feelings for his own brother. The only difference was that he really, truly loved Papyrus in every possible sense of the word - he was his brother, his best friend, his companion for the majority of his life and wanted him to be so for the rest of their lives.

With Blue, it was curiosity and lust. He was different enough from Sans to feel that he wouldn't necessarily be sleeping with himself, but he was still a Sans... Damn, was he a pervert.

Which was why his eyes were glued a little too heavily to the stage as Blue began swaying his body with the techno beat his chosen song was to.

_"If you're alone and you need a friend,_

_Someone to make you forget your problems."_

 

Blue went to the side of the stage where all of his friends sat.

 

_"Just come along, baby, take my hand."_

 

His outstretched hand could have been to anyone at the table, but his huge, bright blue eyes were locked to Sans.

 

_"I'll be your lover tonight!"_

 

He winked as his pupils turned to hearts.

Blue returned to the center of the stage, continuing the song and his seductive dancing, making the room go wild.

But Sans didn't hear any of it, his ears were deaf and eyes were glued to the doppelganger on stage and wondering if the wink wasn't just his imagination. He was also thankful that the room was pretty dark, so no one could see the blush creeping across his cheeks.

It didn't help that when the song ended, Blue went to the other side of the stage to return to the table, which meant he had to pass Sans and he could swear there was a brushing of fingers across his shoulders as he went.

He was going to need a long, cold shower when they got home.

\------

_Sans groaned as he sank into a deep, tight heat. He loved the fingertips that brushed over his ribs and sternum, the breathy moans from the body under him fueled the fire burning within him.  
_

_"More, Sans, deeper, I need to feel you," a voice begged, pulling him down.  
_

_Sans followed, pressing a skeleton kiss to an eager mouth, and opening his eyes to stare into big, blue eyes set into a familiar skull..._

\------

  
Sans sat up with a gasp. His clothes were damp with sweat, his whole body ached, and there was a pale blue glow coming from his shorts.

"Oh, for fuck's sake," he muttered.

But he was still plagued by visions of his double and decided that as long as it was fantasizing, it was fine, and even though he was touching himself and bringing his dream back to the front of his mind, he was soon dozing, leaving his body to act on its own.

~~~~~~~~~~~~~~~~~~~~~

Blue always had some issues falling asleep. He also didn't run on much anyway, so he ended up awake for most of the night doing chores. He didn't care that it wasn't his house, he knew Papyrus would appreciate his efforts, unlike his brother. He decided to go upstairs to the bathroom - maybe he could clean up something in there. But as he approached the bathroom door, there were noises coming from Sans' room.

"What if he has nightmares, like my bro?" Blue wondered to himself. "Well, the Magnificent Sans knows how to take care of nasty old nightmares!"

He moved quietly but confidently towards Sans's door, but another noise from inside made him freeze.

"Blue, oh stars, you feel so good," Sans moaned.

Blue blinked. He had been flirting with Sans all night, and while he enjoyed making his double blush, he didn't reciprocate in any way so Blue assumed that he wasn't interested or that he only had eyes for Papyrus.

Oh, sure, Blue could tell easily. He wondered if either of them knew their brother was insanely in love with the other.

Blue watched in fascination as Sans writhed in bed, his hips hitching up slightly as one hand rubbed over the glow he could easily see through the cloth of his shorts. His other hand was under his shirt, either touching his ribs or maybe even his soul? Blue couldn't quite tell.

"Well, if he's dreaming about me, maybe he wouldn't be opposed to a helping hand," he murmured.

Blue quietly entered the room, making sure to shut and lock the door behind him. He quietly picked his way over Sans' piles of clothes and garbage, being sure to dodge the treadmill in the middle of the room, and soon found himself standing by his bed. He watched Sans for a moment longer, calculating his next move before waiting for an opening to climb into the bed.

Blue took Sans' right hand as it slipped out from under his shirt, their fingers intertwining easily, and he pressed it into the pillow next to his head. He bent over him and let his pale blue tongue reach out and trace the edge of his mouth before Sans moaned and Blue dipped inside. It didn't take long for Sans' magic to pick up and form his tongue too, the slightly darker blue twisting with the pale blue and Blue couldn't help moaning himself.

Consciousness slowly returned to Sans and after a moment of their tongues dueling for control and exploring one another's mouths, his eyes began to slowly open and meet Blue's giant, innocent blue ones.

Sans gasped and tried to scramble away, but Blue had his right hand pinned and he brought up the other to cover Sans' mouth.

"Shh, Shh, it's okay, Sans, it's just me," Blue murmured gently.

Sans calmed, but only slightly. How much did Blue hear or see? It must have been a good amount since he had been kissing him and Sans' left hand was down the front of his shorts. He removed it quickly as his face flushed blue.

"Looks like you were having quite the interesting dream," Blue said with a small smirk. He glanced down and noticed Sans had taken his hand out of his pants, but the blue magic was still very much present.

Sans blushed and looked away.

"There's nothing to be ashamed of, you know, and actually, it's probably my fault that you're having a wet dream about me," Blue murmured, the hand pinning Sans brushing down his arm and across his clavicle. "Probably wasn't too nice of me to tease you all night at the karaoke place."

His finger traced down his sternum; even through his shirt Sans could feel the warmth from Blue's bones and he arched into the touch slightly with a small whimper.

"Oh, my, you do seem rather pent up," he continued, his fingers tracing his ribs to his side before brushing down to his middle. "I'm up for lending a helping hand," he suddenly brushed his hand over the front of Sans' shorts, making his hips buck and another moan vibrated against his other hand. "Of course, no pressure."

Blue backed away, dragging his one hand over Sans' hip, the other caressed his cheekbone before pulling away.

Or at least, he tried to.

Sans had grabbed his wrist and pulled him close. He couldn't think of any words to say so he just clanked his teeth against the other.

Blue didn't expect the sudden yank, but he gladly melted into the kiss, reaching up to cradle Sans' face in his hands. After a moment he reached out with his pale blue tongue and swiped it against the lower ridge of Sans' mouth. Much to his delight, Sans moaned, his tongue darting out briefly to touch against his.

"Mmm," Blue murmured, pulling away for a moment. "There's a pretty big leap between dreams and reality, Sans. Are you sure you want this?"

"Don't you?" Sans asked.

"Well, it's a little obvious I do, don't you think? But I just don't want to give you any hang-ups if you have eyes for someone else."

Sans blushed. "I don't know what you mean," he mumbled, looking away.

Blue giggled. "I know you have at least a crush on your Papyrus. Can't say I blame you, I think he's just about as adorable as one can get."

Sans' blush deepened and he bowed his head.

Blue looked at him with sympathetic eyes and reached a hand out to tilt his face back up. "I came to you for a bit of fun, that's all. Don't get me wrong, I like you and I care about you, but I'm not looking for you to declare your undying love for me or anything."

Sans looked at him carefully. "So, friends with benefits?"

"More like brothers with benefits, but yeah, if that works for you?"

Sans hesitated a moment, then nodded, and Blue pressed forward with a deep kiss. Sans moaned into his mouth, letting the slightly smaller skeleton press him back into his pillows. As their tongues pressed and slid against one another, Blue brushed his hands down Sans' neck, across his clavicles and shoulders and down his arms. He gripped onto Sans' hands and brought them up to the side of his head, pinning them against the pillow as he pressed their bodies together. Sans moaned into his mouth, his eyes fluttering.

"Mmm, you like this?" Blue asked, rocking his hips against him.

"Y-yeah, feels real nice," Sans replied in a whisper.

"Good. I kinda figure you'll like the same things I do," Blue ducked his head and drew a line up the side of Sans' neck with his tongue, making the other gasp. "Yeah, that's a pretty sensitive spot on me, too."

Blue pulled the neck of Sans' t-shirt a little to lap at his collarbones before nibbling on them. Sans wriggled under him with a very small whimper.

"Come on, take your shirt off, I'll take off mine," Blue whispered, leaning back to do just that.

Sans sat up as soon as his hands were released, and while Blue was pulling his shirt over his head, Sans smirked and surged forward and rolled over, switching their positions. Blue squeaked, wiggling the rest of his way out of his shirt while Sans straddled his thighs. The big blue eyes looked up at the other, watching hungrily as he stripped off his shirt.

"You make that look really good," Blue murmured.

Sans blushed a little, his cheeks turning the same medium blue as his tongue. Blue chuckled, wondering if he could make Sans blush even more. He stretched his arms up, arching his back a little, before tucking one arm under his head and trailing the other down his own ribcage. Sans watched in awe as the other fondled his own ribs, tracing a fingertip down his sternum, his thumb drawing circles around the edge of his bottom-most rib.

"See something you like, Sans?" he asked, his voice growing heavy with desire, relishing in the way Sans was staring at him.

Sans nodded, and he reached forward with his own hands to trace down the bones the way Blue had done. He blushed more at the breathy moan Blue let out and the arching of his back.

"It always feels so much better when someone else does it," Blue murmured in appreciation.

Sans smiled, his hands moving lower, reaching to trail his fingertips along the spine above his hipbones. Blue pressed his head back with a groan.

"Oh, stars, is that a sensitive spot," he moaned.

Sans continued to run his fingers over the vertebrae, enjoying how the other squirmed and moaned below him. It must have been a really, really sensitive spot, because he could see a bright glow coming from beneath Blue's shorts.

The pale blue glow turned brighter as Sans curled his fingers over the waistband. He glanced up in question and Blue gave him an encouraging nod. He pulled down his shorts, but then he gasped and backed away.

"Uh, Blue?"

"Hm?"

"Uhm... Why... I thought..."

Blue sat up with a small frown. "Sans?"

Sans was blushing furiously. Blue tilted his head before glancing down his body. His magic had manifested as a vulva, and it took a moment to realize why Sans looked so uncomfortable.

"You never made a pussy before?" Blue asked.

Sans shook his head and tried really hard not to stare at it.

"Mweh heh, sometimes it does it on its own," he explained.

"But, aren't you a dude?" Sans asked.

"Yes. But hey, what's the point of magic if you don't learn its full potential?" He smiled kindly at Sans. "Give it a try. It's a little more complicated than a dick, but I find it feels incredible in its own way."

Sans just nodded, but he didn't seem to be as uncomfortable anymore.

"Don't worry, we'll take it slow, I'll teach you- Eep!"

Blue was cut off by Sans gripping his pelvis and yanking him down. He bent over him, his tongue lengthening and swiping across Blue's outer lips.

"This isn't new territory for me," Sans murmured, looking up at him with a lewd gleam in his eyes. "Maybe I'll teach _you_ a new thing or two."

Sans bent down again, his hands running along the inside of Blue's femurs and he could feel the other shuddering with anticipation. Sans used the tip of his tongue to gently press along the outside of the labia, his fingers caressing the edges of Blue's pelvis. He dipped his tongue in further, massaging and pushing away the folds as he brought one hand over Blue's leg to stroke softly over his clit.

Blue let out a long, soft sigh, wriggling a little under Sans' soft and slow attentions. Just as he was on the verge of asking for more, Sans' finger starting circling his hole and he moaned when he slipped it slowly inside.

"How is it?" Sans asked.

"Fantastic," Blue breathed. "Sans, it's so good."

Sans smirked and returned to his task. He twisted his finger inside Blue, feeling him get more and more wet as he moved his tongue up to replace the fingers circling the sensitive nub of flesh. Blue's breath came out in quick pants, one hand curling on the back of Sans' skull but not pressing, the other hand clutching the edge of the blanket.

"You're getting so wet," Sans murmured. "And I barely got started."

Before Blue could clarify, Sans pushed two more fingers inside him and curled them up at the same time as he licked harder and faster on his clit. The skeleton under him squirmed and whined, the hand clutching the blanket slapped over his mouth with a _clack!_ in an effort to keep himself from getting too loud. This only spurred Sans on and he moved faster, feeling Blue's legs shake by his shoulders, the squelching sound of his fingers moving in and out of him, the taste of his arousal...

"Wait, wait," Blue finally mustered the control to say. "Sans, stop, wait."

Sans froze for a moment and looked up. "Are you okay?"

He was met with Blue's flushed, smiling face. "Absolutely, but I want you to try it, too."

Sans looked confused. "Try what now?"

Blue smiled, easing himself off Sans's fingers, he shifted until he was sitting on his knees. He brought Sans' hand up to his face, pale blue juices covering it, and licked it once.

"I want you to try having a cunt of your own," he murmured in Sans's ear.

Blue's tone and hearing such lewd words coming from the mouth that constantly reprimanded his brother for foul language made Sans shudder.

"I-I d-don't know if I can," Sans stammered, finding the confidence he had before vanished.

Blue chuckled and pushed him back. "Come on, just try, I'll help you."

As Sans' back rested against the balled-up sheets on the corner of the bed, he decided to give in to his curiosity and arousal and he nodded in agreement.

"Mweh heh, knew you'd want to," Blue murmured, leaning in to drag his tongue against Sans' teeth, begging for entry.

Sans' tongue met his, they danced and dueled for control, though Sans was losing as he was distracted by wandering hands pressing against his hips as his shorts were pushed down. Once his pelvis was exposed, Blue started to touch him gently. Sans noticed he was brushing his fingers ever so slightly across the sensitive bones, taking care to run one or two fingers up and down the center.

"I discovered that at first, it matters where and how you're touched," Blue murmured against his mouth. "But of course your thoughts mean just as much. You know what mine looks like; soft folds like the petals of a flower, a clit begging to be touched and teased, a hole dripping with want."

Sans closed his eyes as Blue murmured his description, the words adding fuel to the fire building under the hand stroking his pelvic bones. He felt his magic gathering and slowly manifesting into something solid.

"Oh, Sans, it's beautiful," Blue murmured, one hand curving under Sans' jaw. "Look for yourself."

Sans cracked an eye open to see the blue mound his magic conjured. He couldn't really see much but the warm sensations pulsing from it were so pleasurable he didn't mind.

"Mind if I explore?" Blue asked.

Sans shook his head.

"You're going to love this," Blue murmured against his neck before nibbling on his bones.

Sans moaned at the sensations at his neck, but positively gasped when Blue's fingers swiped up his slit. Everything felt overly-sensitive, the bony fingers caressed the folds of magic, circled the hole that was just starting to moisten, and rubbed gently over the bundle that shot a bolt of pleasure up Sans' spine.

"Feels good, doesn't it?" Blue murmured.

"Aaah, uh huh," Sans moaned, unable to articulate more than that.

"If you think this feels good, just wait until someone is inside of you. Would you like that, Sans?"

Sans stared up at Blue, face flushed and incredulous - was he really expecting him to say no? He couldn't quite gather the ability to say yes, either, so he nodded as he fidgeted under Blue's wandering fingers.

Blue smiled. "I figured you would, Sans." He leaned down and kissed him deeply as he easily slid a finger into his dripping hole.

Sans' hips bucked up as he gasped at the sensation, kissing back with all of his might as if to distract him from the new feelings between his legs. Blue began to copy what Sans did to him earlier, his fingers exploring, caressing, and Sans was already so wet that using his tongue wasn't very necessary. Blue slowly slipped his middle finger into Sans' tight hole, using the heel of his palm to rub against the rest of his pussy while he gently pumped him.

Sans moaned into his mouth, his eyes opening a little to see what was causing the wonderful feeling. Blue smirked, seeing that he was watching, and slipped in a second finger. Sans whimpered and squirmed, his heels digging into the mattress.

“Mmm, stars you make such wonderful sounds,” Blue murmured against the side of Sans’ skull. “Shh, listen for a second.”

Sans swallowed his next vocalization and listened; the wet sounds of Blue’s fingers moving in him reached his ears, making him blush even more.

“Heh, and people say I’m the cute one,” Blue murmured, moving his fingers faster.

“Nngh, aaaaahhhh,” Sans moaned, screwing his eyes shut.

“Feel good?”

Sans nodded vigorously.

“If you think that’s good, give me a moment.”

Blue pumped him a few more times before slowly drawing his fingers out, sliding up to brush over his clit with the warm, wet digits. Sans was breathing heavily, caught between missing the wonderful strokes and thankful for the reprieve. He barely noticed Blue settling between his legs and only opened his eyes when he felt those hands run along the inside of his legs. He noticed the pale blue glow and his eyes widened slightly as the impressive appendage that Blue had between his own legs. Noticing he was being watched, Blue smirked and stroked himself a few times.

“Are you nervous?” he asked with a slightly teasing lilt in his voice.

“A-a little,” Sans admitted.

Blue smiled, reaching with his other hand to run his fingers along Sans’ pussy.

“That’s to be expected. You can of course change your mind,” Blue said.

“No, please, I want it,” Sans murmured.

“As long as you’re sure,” Blue murmured.

He moved closer and rubbed the head against the magical folds.

“Mmm, please, please don't tease me,” Sans whined, moving his hips up.

“Easy, easy, I don't want to hurt you,” Blue murmured. “Just let me know if you need me to stop.”

Sans gasped as Blue's cock breached his opening. It didn't hurt, really, but he did feel every centimeter as Blue slowly pushed inside of him.

“Ah, ah, unh,” Sans gasped.

“Are you all right?”

“Yeah, please, more.”

“As you wish.”

Blue slid inside the rest of the way and the both shared a gasp of pleasure at the sensations; Sans was almost overwhelmed by being filled and having every sensitive spot being brushed upon inside of him and Blue reveled in the tight, wet heat with soft surfaces fluttering over his shaft. Blue leaned down to touch their foreheads together.

“Stars, do you feel good,” Blue murmured.

Sans could only moan in response, rolling his hips up slightly, bringing Blue into him more. Blue groaned and leaned down to capture Sans' mouth in a kiss while he began to thrust into him slowly. Sans' hands reached up to grip him by the shoulders, trying to control his breathing as the sensations began to slowly consume him.

After a few moments, Blue began to pull out a little further before moving back inside, soon reaching the point where he was pulling nearly all the way out before thrusting back in. Sans writhed beneath him.

“Please, more,” he moaned, looking up with pleading eyes.

Blue smirked, pulling nearly all the way out again, but this time he slammed back into Sans, whose hand flew to his mouth to muffle his wail. Blue started a quicker, steady pace, reaching down with one hand to caress Sans' ribcage.

“You're so sexy, Sans,” Blue murmured. “Especially having you beneath me like this? It's such a turn on that I'm the one putting that slightly desperate look into your eyes.”

Sans wondered if a skeleton could die from too much blushing, because this time it flowed all over his body. He turned his face away, screwing his eyes shut, his hands moving as if to cover himself.

“Heh, you're just like my brother; you both have a difficult time accepting compliments,” Blue said with a chuckle, moving to grip Sans' hands gently and pinning them to either side of his head. “Look at me, Sans.”

Sans was compelled to look into the large blue eyes staring him down. He almost laughed because Blue's pupils were still shaped like hearts, but the smoldering look he gave him took any silly humor out of the situation.

“You are amazing in so many ways. Whatever is in your head that makes you think otherwise needs to take a long walk off a short cliff.”

He bent down to kiss Sans again, the movement between their pelvis' had slowed back to a gentle, rocking, shallow pace. Sans kissed back with a sigh, nodding slightly at Blue's words.

“Now, I'm going to bang you and make you cum so hard,” Blue said in a promising tone.

Sans rolled his hips up, desire sparking again. “Stars, please,” he whispered.

Blue started moving again. He released one of Sans's hands to reach down to grab his leg, lifting it so it leaned against his hipbone. The change in angle allowed Blue to go in deeper, hitting a spot that made Sans cry out.

“Ah, there it is,” Blue murmured, shifting slightly and making sure he hit that spot with every thrust.

Every time the spot was hit, it sent waves of electricity up Sans' spine, making him roll his hips up with each thrust, increasing the friction and pleasure for them both. He could feel his orgasm building, slowly but steadily, making him borderline desperate for release.

As if he could sense this, Blue released Sans' other hand and reached down to rub circles over his clit.

That did it; Sans' orgasm crashed over him like an avalanche. His back arched only a little as Blue kept a hold of him, Sans' hands flying to his mouth to contain his wail of pleasure. Blue rode him through it, following him a minute later, spurned on by the wonderful sight of the skeleton cumming beneath him.

All at once Sans' body went limp; he lost his senses for a moment, but he came back to himself as Blue dropped soft kisses all over his face.

“Are you all right?” Blue asked.

Sans nodded, lifting shaking hands to wrap around Blue's shoulders.

“Are you sure?”

Sans pulled him down and kissed him, running his tongue along his teeth.

“That was fucking amazing,” Sans murmured.

“Language,” Blue admonished him.

They held each other for a while, dropping soft kisses on one another as their bodies cooled and the magic dissipated.

“I think you'll be able to sleep a little easier now,” Blue said, pulling up the blanket and almost like he was moving away.

Sans gripped him. “Will you stay?”

Blue looked down at him. “Are you sure?”

“Yeah. Please?”

Blue smiled, pulling the blanket over them both and snuggled into the other skeleton.

“Good. I like cuddling.”

Sans chuckled. “Yeah, me too.”

“So now you have a new trick for when you finally admit your feelings to your brother.”

Sans' blush returned. “Go to sleep, you marshmallow.”

Blue snickered, giving Sans one more kiss before they fell asleep.

 

**Author's Note:**

> Come visit me on my [TUMBLR!!!](https://www.tumblr.com/blog/soloshikigami)
> 
> Oh, and the song Blue sings? Here you go:  
> [ Boom Boom Boom by The Venga Boys](https://www.youtube.com/watch?v=FU-9kt-qi1g)  
> Yes, I have totally carbon-dated myself -_-


End file.
